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PGI-1 Talk: Dr. Sumit Ghosh

Non-equilibrium transport in topologically nontrivial systems: Application to spin-orbit torque

24 Jan 2019 11:30
Seminar room N-142

KAUST, Saudi Arabia


Topological insulators do not need any introduction nowadays. They can be distinguished from the normal insulator, metal or semiconductors by their robust surface/edge states which are immune to the various type of perturbations. Among different classes of topological insulators, the Z2 topological insulators (e.g. Bi2Se3, Bi2Te3) draw special attention for their strong spin-orbit coupling which makes them a promising candidate for spintronics applications, especially for magnetic memory devices. Owing to their superior spin-charge conversion efficiency, a topological insulator based spin-orbit torque device can operate with two orders of magnitude smaller switching current compared to their heavy metal counterpart.

Although their superior performance is well established, the underlying physics is still in mist. The existing theories can describe a clean topological insulator surface which does not hold when it is sandwiched with a magnetic material. In this presentation, we are going to address these issues in a heuristic way. By using a minimal tight binding model with linear response theory, we explain the non-equilibrium transport properties of a magnetic topological insulator as well as a heterostructure made of a topological insulator and a ferromagnet or antiferromagnet. We are going to show how the topological insulator and the magnetic element exchange their mutual properties depending on different system parameters giving rise to the new features of the band structure and the interfacial spin texture which in turns govern the non-equilibrium spin density. Finally, we demonstrate the topologically nontrivial characteristics of different physical observables from their dependence on the impurity scattering.


Prof. Dr. Yuriy Mokrousov
Phone: +49 2461 61-4434